Physics (AS & A Level) · Oct / Nov 2016 · Paper 22 · Question 4
9702
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4(a)[2]
wave incident on/passes by or through an aperture/edge wave spreads (into geometrical shadow) [2]
4(b)(i)[2]
waves (from slits) overlap (at point X) path difference (from slits to X) is zero/ phase difference (between the two waves) is zero (so constructive interference gives bright fringe) [2]
4(b)(ii)[1]
difference in distances = λ / 2 = 580 / 2 = 290 nm [1]
4(b)(iii)[3]
λ = ax / D D = [0.41 × 10–3 × (2 × 2.0 × 10–3)] / 580 × 10–9 = 2.8 m [3]
4(b)(iv)[2]
same separation/fringe width/number of fringes bright fringe(s)/central bright fringe/(fringe at) X less bright dark fringe(s)/(fringe at) Y/(fringe at) Z brighter contrast between fringes decreases Any two of the above four points, 1 mark each [2]
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